Weight is the single most objective number you have for whether feeding is working. It also generates more parental anxiety than almost anything else in the first month. Once you understand the normal pattern — including the dip everyone forgets to mention — you can stop reading scales like tea leaves and start reading them like the trend graphs they actually are. For a wider view, see our complete guide to child health.
The Normal Dip and Climb
Almost every newborn loses weight in the first three to five days. That isn't a feeding problem; it's physiology. Babies are born with extra fluid on board, mature breast milk doesn't fully come in until around day three, and the gut is still adjusting to enteral feeding. A loss of up to 7% of birth weight is unremarkable. Up to 10% is still considered within normal limits, with the caveat that a baby down 10% gets a closer look at feeding technique and milk transfer.
After the lowest point — usually somewhere between day three and day five — babies climb. Most are back to birth weight by day 10 and almost all by day 14. From there, the rough rule of thumb is:
- 0–3 months: 150–200 g per week
- 3–6 months: 100–150 g per week
- 6–12 months: 70–90 g per week, slowing further as activity ramps up
These are averages. Some babies put on 250 g in a good week and 80 g the next, and that variability is fine as long as the medium-term direction is right.
How the Centile Chart Actually Works
In the UK, weight goes into the red book (the Personal Child Health Record) and gets plotted on a WHO-based centile chart. The line you're looking at is essentially a percentile rank: a baby on the 50th centile is bigger than half their peers; one on the 9th centile is bigger than 9% of them.
The single most common misreading: parents see a low centile and panic. A low centile is not a failing grade. A baby tracking steadily on the 9th centile is growing at a healthy 9th-centile rate. The thing to watch for is a baby who crosses two centile lines downward — for example, born on the 50th and now sitting on the 9th over six weeks. That pattern triggers a feeding review and possibly a developmental check.
WHO charts (the standard since 2009 in the UK) were built using exclusively breastfed babies as the reference population. Older formula-derived charts often made breastfed babies look like they were "falling off" their line at four to six months. The newer charts solve that.
Who Weighs the Baby and How Often
The midwife is the lead professional for the first 10 to 14 days. They'll usually weigh at the day-five heel-prick visit and again towards the end of their care. After handover, the health visitor takes over. Routine weight checks are offered at:
- 10–14 days (often combined with a feeding review)
- 6–8 weeks (alongside the GP baby check)
- 8–12 weeks (ahead of immunisations)
- Then at 4–6 months, 12 months, and 2–2.5 years for development reviews
Most clinics are happy to weigh more often in the early weeks if you want. Weekly is reasonable. What's not useful is daily or twice-daily weighing — the swings in fluid balance from feed to feed can show ±100 g changes that mean nothing about actual growth. Weighing before-and-after a feed to estimate intake is similarly unreliable in most situations and tends to undermine breastfeeding confidence rather than help it.
What to Watch Alongside the Number
The scale is one data point. Use it together with these:
- Wet nappies. From day five or six, expect six or more genuinely wet nappies in 24 hours. A useful test for whether a disposable is "wet enough": pour about 30 ml of water onto a clean nappy and feel the weight — that's roughly what a wet nappy should feel like.
- Stools. Frequency varies hugely. Breastfed babies often go several times a day in the first weeks; once feeding is established (after week four), some breastfed babies stool once every three to five days and that can be normal. Formula-fed babies are more predictable, with one to three stools a day.
- Behaviour at feeds. A well-fed baby comes off the breast or bottle relaxed, hands open, looking sleepy or alert. A baby who finishes every feed crying may not be getting enough.
- Wake-and-feed pattern. In the first two weeks, a baby sleeping more than four to five hours without waking for a feed is unusual and worth waking. After that, longer gaps are fine if growth is on track.
When to Get Help
Speak to your midwife, health visitor, or GP if:
- Weight loss is more than 10% of birth weight at any point
- Birth weight isn't regained by day 14
- Weight crosses two centile lines downwards
- The baby is jaundiced and feeding poorly
- You're getting fewer than six wet nappies in 24 hours after day five
- Feeds are painful (for you), short, or the baby is repeatedly distressed afterwards
Earlier is easier. A feeding problem caught at day six is usually fixable with a tongue-tie check, position adjustment, or supplementation; the same problem at day 21 has often started to affect milk supply.
When the Worry Is "Too Much"
High birth weight or rapid early gain occasionally raises questions about overfeeding. Breastfed babies are very hard to overfeed — they self-regulate well. Formula-fed babies can be overfed, but the answer isn't to dilute the formula (don't do that — it's dangerous) or to ration intake. The answer is responsive feeding: pacing the bottle, watching for fullness cues (turning away, slowing the suck, relaxing the hands), and stopping when the baby is done rather than finishing the bottle on principle.
Ultimately the chart is a guide, not a verdict. A baby who is feeding, weeing, sleeping, and looking at you with interest is almost certainly fine. The numbers are there to flag the rare times when something needs adjusting — not to be checked for reassurance every Tuesday.
Key Takeaways
Most healthy newborns lose 5 to 10 percent of their birth weight in the first three to five days, then climb back to birth weight by day 10 to 14. After that, expect roughly 150 to 200 grams a week for the first three months. The trend on the centile chart matters far more than any single weigh-in. Six wet nappies a day from day five, regular stools, and a settled baby after feeds are the practical signs that things are on track. Weighing more than once a week is rarely useful and often counterproductive.
